The navel orangeworm, Amyelois transitella (Walker), is the most serious field insect pest of almonds in California. Growers lost about $24 million to this insect in 1977, an average of $87 per bearing acre.
Several researchers have tested a variety of substances for attracting female moths to a trap. Rice et al. (1976) reported on egg traps baited with a mixture of wheat bran, glycerine, honey, and water that both attracted female moths and stimulated oviposition. (Rice, R. E., L. L. Sadler, M. L. Hoffman, and R. A. Jones, 1976. Egg traps for the navel orangeworm, Paramyelois transitella (Walker). Environmental Entomology 5: 697-700.) In an effort to find a substance that could be used to attract navel orangeworm moths to traps, Price et al. (1967) screened about 225 organic compounds and found phenyl propionate the most efficacious. (Price, D. W., J. A. Mazrimas, and F. M. Summers, 1967. Chemical attractants for navel orangeworm moths. Calif. Agric. 21(11): 10-11.) Five other compounds that consistently showed a relatively high degree of attractiveness were phenyl isobutyrate, phenyl-2-propanone, phenyl ether, .alpha.-methylbenzyl alcohol, and ethyl phenylacetate. About 90-95% of the moths attracted to these chemicals were female.
The attraction of female A. transitella to previously damaged host material (walnuts) was noticed by Ortega (1950). (Ortega. J. C. 1950. The navel orangeworm on walnuts in southern California. Diamond Walnut News 32(5):6-7.) Later Caltagirone et al. (1968) and Curtis and Barnes (1977) reported that female moths deposited 2.4 and 2.0-fold, respectively, more eggs on previously infested than on uninfested old nuts. (Caltagirone, L. E., D. W. Meals, and K. P. Shea. 1968. Almond sticktights contribute to navel orangeworm infestations. Calif. Agric. 22(3):2-3.) (Curtis, R. K., and M. M. Barnes. 1977. Oviposition and development of the navel orangeworm in relation to almond maturation. J. Econ. Entomol. 70. 395-8.) These data apparently indicate that host odors may be more important than are tactile stimuli in the oviposition behavior of A. transitella. However, when Post et al. (1959) investigated whether the navel orangeworm was a pest of stored almonds, they concluded that almonds were not much more attractive to the female moths than were the building materials of the cage used in the test. (Post, G. R., D. J. Hurlebaus; and F. M. Summers. 1959. Tendencies of navel orangeworm infestations in almonds. Almond Facts 24(1): 4, 12.) Also, Wade (1961) reported that large numbers of navel orangeworm eggs were occasionally laid on twigs several inches from the nearest nut but never on branches or leaves. (Wade, W. H. 1961. Biology of the navel orangeworm, Paramyelois transitella (Walker), on almonds and walnuts in northern California. Hilgardia 31(6): 129-71.)
A great deal of published information concerns the use of insect sex pheromones to disrupt communication between male and female insects of the same species so that they cannot find one another for the purpose of mating. For example, see Andrews, Keith L. and Martin M. Barnes, 1982, Differential Attractiveness of Infested and Uninfested Mummy Almonds to Navel Orangeworm Moths, Environmental Entomology 11:280-282, and Buttery, Ron G., E. L. Soderstrom et al., Components of Almond Hulls: Possible Navel Orangeworm Attractants and Growth Inhibitors, 1980 Agricultural & Food Chemistry 353-356, and Buttery, Ron G., R. M. Seifert et al., 2-Hexyl-3-methylmaleic Anhydride: An Unusual Volatile Component of Raisins and Almond Hulls, 1980, Agricultural & Food Chemistry 28:1336. Further, see Carney et al. U.S. Pat. Nos. 4,198,533, Apr. 15, 1980 and 4,228,093, Oct. 14, 1980. There are a number of commercially available such products.
Other research (Curtis, C. E., and Clark, J. D., 1979, Response of Navel Orangeworm Moths to Attractants Evaluated as Oviposition Stimulants in an Almond Orchard, Environmental Entomology 8:330-333.) was designed to determine whether extracts of frass, larvae, and almond-fruit-parts contained attractive substances that could be extracted by using several different solvents.